Inflatable Diving Boat - which motor Should I go with - 2 stroke vs. 4 stroke?

[zboss]

JT2 once bubbled...
I agree with just about everything here accept for the above statement. The 4-stroke is going to have a broader though lower rpm torque curve, which will allow it to pull a higher pitched prop in the lower rpm range thus giving it more bottom end and this also makes it better suited for heavy loads. Simply saying that you need less horsepower with a 4-stroke is not exactly true for every application, although I think in LoriP's situation the 4-stroke would be the best choice if they can lug it around. I am not a fan of 2-stroke eegbeaters, but pound for pound they can't be beat.

Absolutely I agree - different engines are good for different applications. In general I have found that for beating across open water my Yamaha 90 HP 2 stroke wasn't nearly as good as my Honda 75 HP 4-stroke.

 

[LoriP]

In reply to Heman (I'm not sure how you all put those "quotes" on these threads).

Anyway, our 10' inflatable will only hold a 15 hp max. On low HP 4 stroke outboards, the different in weight between a 2 stroke and 4 stroke is large. A 15 hp 4 stroke motor weights about 115 lbs. , whereas a 2 stroke is about 70 lbs. The lightest 4stroke I've found is a Yamaha at 99 lbs. 9.9 hp 4-strokes are only about 5 lbs. lighter than the 15.

We're definately going with a 4-stroke now.

 

[sailnj]

2 - Strokes are still considered to be much less problematic in the repair department than 4-strokes. Also, the weight is a big factor. If you plan to use the boat and motor outside the continental US you can forget about ever getting parts to repair your 4-stroke. 2- strokes are much cheaper and there is also a much larger used parts market (which is also important if something major goes since many times replacement new parts can cost almost as much as a new motor) All that said if you go with the tree huggers suggestion then I would highly recommend a Yahama - they build very reliable and durable uncomplicated engines. This month's Practical Sailor magazine reviewed small four strokes if you want an un-biased opinion (they have no advertising)

 

[etype]

'outside the continental us' you won't be able to find parts?

Sure..., honda, yamaha, mariner only sell 4-stroke parts to americans...
I think anyone who feels any responsiblity for the enviroment would agree that unless absolutely necessary a 4stroke is the way to go. I have a 25 hp Honda on my Zodiac (in canada no less)...i;ve had meriads of different outboards in every horsepower range...and i have to tell you...4 strokes are sweet in every regard. 2strokes are not ony enviromentally messy, but they make a hell of a lot more noise and mixing oil/gas for fuel is not a fun thing to do compared to just gas .
Go with 4 stroke, you will be thankful you did.

 

[kavka]

4 stroke Yamaha (high trust) weights the same as old 25 2 stroke, but wouldn't trade any more. 4 stroke runs without any problems 2 stroke !?...

 

[DennisS]

How much lifting/carrying of the engine are you going to be doing. I have a 25 hp 2 stroke on my 12 foot, curse it every time I move it and wish I'd bought a 15 hp. What's your back worth.

 

[zeN||]

Your engine size is related to the rating on your boat, which should be stated on the plate on the transom. I just got this 9.9 hp 2 stroke for my achilles and you can bet it's going in the water! ~Z

 

[nwdiver2]

4 stroke as you know the 2 strokes a present can not be purchased in some places and in the next few years will be illegal in many places.

 

[100days-a-year]

2 strokes are not going to be illegal in 2 many places as the newer DI 2 strokes burn very clean.4strokes are heavier ,slower, no NOT have any fuel consumtion advantage and have more moving parts to fail and need adjustment.DI technology has revolutionized 2 stroke motors and every year the engines avaiable with it are getting smaller.Try some boating/sailing websites on comparisons,also the motor manufacturers have actual tests of thier motors on various boats on thier websites.